Ultra high frequency antenna



G. H. BROWN ULTRA HIGH FREQUENCY ANTENNA July 16, 1940.

Filed May 1958 Ytlorneg Patented July 16, 1940 UNITE-D sT TEs ULTRA HIGHFREQUENCY ANTENNA George H. Brown, Haddonfield, N. J.," assignor toRadio Corporation of America,,a corporation of Delaware v ApplicationMay 28, 1938, Serial No. 210,605

4 Claims. 01. zso ssi My invention relates to antennas and moreparticularly to an ultra high frequency antenna suitable for theradiation of horizontally polariz ed waves.

It has recently become apparent that horizontally polarized waves atultra high frequencies are more desirable for certain purposes thanvertically polarized waves. One method of 'radiating a horizontallypolarized field of circular pattern is shown in my U. S. Patent No.2,636,- 976, entitled" Antenna Systems, and issued July 13, 1937. Whilethe method there disclosed is highly efficient for producing ahorizontally polarized circular rotating field, in some instances thisrotation is undesirable. Horizontally polarized waves which arenon-rotating may be obtained by an antenna constructed according to thisinvention.

It is highly desirable that the elements of an antenna be rigidlymounted. High frequency antennas are readily adaptable to the use ofrigid rods as conductors because resonant lengths are not unduly long.The question of rigidly supporting such an antenna usually involves aconsideration of the problem of supplying suitable insulation from thesupporting medium.

It is, therefore, an object of this invention to provide an antennawhich may be rigidly supported, and which does not require insulationfrom its supporting medium.

It is a further object of this invention to provide a high frequencyantenna which produces horizontally polarized waves having asubstantially circular horizontal radiation pattern.

It is a still further object of this invention to provide means forsuitably phasing the elements of a horizontal loop antenna whereby auniform horizontal radiation pattern is obtained. 7

This, invention will be better understood fro the following descriptionwhen considered in connection with the accompanying drawing. Its scopeis indicated by the appended claims. Similar reference numerals refer tosimilar elements throughout the drawing.

Referring to the drawing:

Figure 1 represents the current distribution in a dipole antenna whichis folded in the form of a square, a half wave length on a side,

Figure 2 represents the current distribution in an antenna when modifiedin accordance with my invention by the inclusion of two quarter waveresonant lines,

Figure 3 illustrates the application of four quarter wave sections to asquare antenna,

Figure 4 is a plan View of an antenna mounted on a supporting mast inthe manner of my invention,-

Figure 5 is an elevation of Fig. i, and

Figure '6 is a plan'view illustrating an alternative antennaconstruction.

In Fig. 1' I have shown an antenna consisting of two full wave sectionsl and 3, each forming two sides ll, l5 and I3,-ll, of a square one halfwave length on'a side. The'antenna is fed by a transmission line 5,which is connected between the adjacent ends of the two sections. At aparticular instant thecurrent flowing through the antenna is asindicated by the arrows. The current distribution along each wire is asshown by the dotted lines. It will be noted thatthe current in twosections is out of phase with that in the other two. Consequently, auniform horizontal radiation pattern will not be obtained.

Accordingly, I propose to open each section I and 3 at its mid-point andinsert in each a quarter wave resonant line I and 9, as shown in Fig. 2.The total length of conductor in each line is a half wave length and isfolded back upon itself; Therefore, undesired out of phase currents flowthrough the section without radiation, and bring the adjoining sectionsI l and I3 into phase with the original sections I5 and H. The newcurrent distribution is therefore as shown in Fig. 2 by the dottedlines.

It is well known that a pair of parallel wires a quarter wave lengthlong shorted at one end present a very high impedance at the open end.Since the voltage distribution between the sections H, I3 and I5, I1 isthe same as that of the sections on either side of the quarter wavesections 1 and 9, it follows that two more similar quarter wave sectionsl9 and 2| can be connected between the sections H, 53 and I5, Il asshown in Fig. 3. The high impedances at the input of these sections donot affect the operation of the antenna, and the desired voltagedistribution is attained.

In a practical application the value of this method becomes evident. Theshort circuited end of each of the quarter wave sections is a voltagenode, and therefore may be grounded without affecting the operation ofthe antenna. Four points of support are therefore provided, and anantenna of great rigidity can be constructed- Figure 4 illustrates apractical method of utilizing this invention. The figure represents atop View of a horizontal antenna consisting of four half Wave sectionsH, I3, l5 and H. By extending the parallel portion of the quarterrounded corners and slightly concave sides.

Wave sections I, 9, l9 and 2|, the may be securely connected to anantenna mast 23, or the like.

Shorting bars 25, 21, 29 and 3| are provided for tuning the respectivesections to resonance. The shorting bars may conveniently be variable.

Fig. 5 is a side view of such an antenna which illustrates howconveniently an antenna of this description can be mounted on a mast.Insulators are not necessary and therefore the maximum strength andrigidity can be attained. The transmission line is also convenientlysupported by quarter wave sections spaced as necessary down the mast.One of these is shown at 33, and is similarly equipped with anadjustable shorting bar 35.

My-invention is not limited to an antenna having four sections but mayconsist of any number of sections. The antenna may have a hexagonal oreven a circular shape, for example, as shown in Fig. 6. In this case,each half wave length section subtends an arc of approximately It can beshown that an antenna constructed according to this invention produces ahorizontal radiation pattern which is generally square with Due to theelimination of insulators the antenna may be economically built andrigidly constructed.

I claim as my invention:

1. An antenna system which comprises a plurality of half-wave resonantradiating elements lying in a plane and positioned so as to enclose anarea, phase inverting means connecting adjacent ends of said radiatingelements to each other, and means including said phase inverting meansfor mounting said antenna.

2. An antenna system which comprises a plurality of half-wave resonantradiating elements a mast, and means including said non-radiatingelements for mounting said antenna on said mast.

3. An ultra high frequency antenna system which includes a plurality ofresonant half wave radiating elements defining the sides of an area inthe horizontal plane, a quarter wave resonant line connecting adjacentends of said elements, a mast for supporting said antenna, and meansrigidly connecting said mast to said quarter wave lines at a point whichis substantially a voltage node, whereby said antenna is supported byand efiectively insulated from said mast.

4. An ultra high frequency antenna system which includes a plurality ofradiating elements positioned end to end so as to define an area, aquarter wave resonant line connectingadjacent ends of said elements, amast for supporting said antenna, and means connecting said mast tosaid.

whereby said

